Cytomegalovirus is a widespread human pathogen with the ability to persist as a lifelong latent infection. Although CMV infection is typically subclinical, life-threatening disease may occur in the immunosuppressed. Our long-term goal is to identify mechanisms used by human CMV to establish latent infection and reactivate from latency. The hypothesis is that CMV-encoded interleukin-10 (cmvlL-10) signaling in monocytes triggers events that may facilitate establishment of or reactivation from latency. This is based on the following: 1) cmvlL-10 binds to the cellular IL-10 receptor (IL-10R), despite having only 27% sequence identity to human IL-10 (hlL-10), 2) cmvlL-10, like hlL-10, has potent immunosuppressive properties, such as down-regulation of MHC expression and inhibition of cytokine production by monocytes, and 3) cells harboring latent CMV express a transcript with homology to IL-10 encoding an alternately spliced form of cmvlL-10 (LA-cmvlL10). Furthermore, the UL111.5A region encoding cmvlL-10 is non-essential for lytic virus replication, suggesting a role for cmvlL-10 in other aspects of virus infection. Based on these observations, the proposed study will more thoroughly examine the effect of cmvlL-10 on monocytes, a site of virus persistence.
The specific aims are: 1) Define signaling events that result from IL-10R engagement by cmv-lL10. We will examine a) activation of Stat transcription factors, b) participating protein kinases, and c) changes in gene expression. 2) Examine the mechanism for cmvlL-10-induced modulation of monocyte function. 1 possible mechanism involves inhibition of transcription factor NF-kappaB activity. To test this, we will examine a) Nf-kappaB activation, b) I-kappaB protein, levels, and c) I-kappaB-alpha phosphorylation state. 3) Determine whether LA-cmvlL-10 has biological function. We will a) express LA-cmvlL-10, b) examine binding to IL- 10R, and c) evaluate inhibition of cytokine production. The results will provide a better understanding of the molecular action of cmvlL-10, and possibly establish a role for cmvlL-10 in regulation of virus latency. ? ?
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